Hydrazine (N2H4) has similar chemical characteristics to those of ammonia (NH3) gas, but is a transparent liquid at a room temperature having the similar melting point, boiling point and density as those of water. Hydrazine has been variously applied to a forming agent for making pores in a polymer, a derivative needed to make agricultural pesticides or medicaments, an oxygen remover from boiler water, a fuel cell, a fuel of a rocket, and so on. Since hydrazine is very poisonous and has high reactivity, it is stored and used in the state of an aqueous solution diluted with water rather than anhydrous hydrazine. Nevertheless, since liquid hydrazine may cause occurrence of fire due to leakage or evaporation or contamination due to rapid reaction with peripheral metals or materials, there has been lots of restriction to its application.
As one solution to the problems of liquid hydrazine, it has been suggested to make and use solid hydrazinium salts in lieu of the hydrazine. The hydrazinium salts can be easily made by adding acids such as sulfuric acid or hydrochloric acid to the liquid hydrazine. For example, when sulfuric acid solution is added to the liquid hydrazine, precipitates are immediately produced and converted into hydrazinium sulfate. These solid hydrazine derivatives are advantageous in that they are in the stable solid phase at a room temperature and can have similar characteristics to those of the liquid hydrazine when they react with other compounds in a solution. However, since the hydrazine salts require a solvent upon reaction, an additional process for separating the solvent after the reaction is necessary. Further, undesired impurities are formed due to residual anions. In addition, since the hydrazine salts exist as a hydrazinium cation in a solution, their reactivity or decomposition ability to generate hydrogen is very poor, compared to hydrazine. Due to the foregoing flaws, application research of the hydrazine salts has been limited, despite that various types of solid hydrazine salts which are highly stable at a room temperature and a normal pressure have been developed.
In order to solve the above-described problems, as disclosed in U.S. Pat. Nos. 3,551,226 and 2,878,103, solid hydrazine was prepared by using carbon dioxide which is flame retardant gas. This method was carried out by blowing carbon dioxide into a cold hydrazine solution at a normal pressure. Once the gas is blown for 15 hours or more, sticky precipitates in which the carbon dioxide and the hydrazine are mixed with each other are gradually produced. However, this resulting product is a solid containing water and mainly consists of carbazic acid (HCO2N2H3) and hydrazinium carbazate (N2H5CO2N2H3). Accordingly, the proportions of the hydrazine and the carbon dioxide are not constant. Further, since the resulting product is very sticky solid, there has been difficulty in obtaining pure solid hydrazine in a powder form through a general drying method.